Methods for High-Throughput Labelling and Detection of Biological Features in situ Using Microscopy

ABSTRACT

Methods of labelling one or more subcellular components (e.g., an organelle and/or subcellular region) in vivo are provided. Methods of labelling a protein in vivo are provided. Methods of determining a nucleic acid sequence in situ are also provided.

RELATED APPLICATION DATA

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/023,226, filed on Jul. 11, 2014 and is hereby incorporated hereinby reference in its entirety for all purposes.

STATEMENT OF GOVERNMENT INTERESTS

This invention was made with Government support under grant number1U01MH098977-01 awarded by NIMH, grant number DE-FG02-02ER63445 awardedby DOE, and R01 MH103910-01 awarded by NHGRI. The Government has certainrights in the invention.

FIELD

The present invention relates to methods and compositions for detecting,identifying, measuring, counting, and/or segmenting biological featuresin cells.

BACKGROUND

Current methods for detecting biological features in cells broadly fallinto three categories: 1) affinity-based detection using synthetic ornatural antibodies conjugated to a fluorescent moiety; 2) fusingbiological features to recombinant fluorescent proteins; and 3)labelling biological features with dyes. These art-known methods enablequantitative detection and localization of target features in fixedand/or living cells in situ. However, methods known in the art at thetime of filing suffer from the drawback of only being able to utilize anarrow range of spectral space for multiplexed detection. Further,methods known in the art at the time of filing are prone to artifactsdue to e.g., autofluorescence and/or noise in the analog signal domain.

SUMMARY

Accordingly, novel compositions and methods for specifically labellingof biological features in living cells, followed by detection ofassociated barcodes in situ using fluorescent sequencing are provided.

Embodiments of the present invention are directed to methods that arebroadly applicable to highly specific multiplex visualization andlocalization of biological features. Unlike technologies known by othersin the art at the time of filing, such as e.g., the use of fluorescentproteins, antibodies, nucleic acid probes, and the like, the methods ofthe present invention provide a subset of possible sequences that can beused to identify individual features. By applying a sequence patternidentification and matching approach to object-based image analysis, themethods described herein enable very high multiplexing capacity, whileeffectively eliminating false positives due to autofluorescence andbackground noise. Biological features (e.g., proteins and nucleic acids,macromolecular complexes, subcellular structures, cells, cellprojections, extracellular structures, cell populations, tissue regions,organs, and other biological structures of interest) can be easilyidentified without relying on low-throughput, manual annotation ortraditional automated image processing methods having limitedsensitivity and/or accuracy.

In certain exemplary embodiments, a method of labelling a subcellularcomponent in vivo is provided. The method includes the steps ofproviding a cell expressing an RNA comprising a barcode, reversetranscribing the RNA to produce DNA, circularizing the DNA, andperforming rolling circle amplification (RCA) to produce an amplicon.The method optionally includes the step of detecting the amplicon.

In certain aspects, the RNA comprises a localization sequence thattargets the RNA to the subcellular component. In other aspects, thesubcellular component is an organelle (e.g., one or any combination of anucleus, a nucleolus, a mitochondria, a Golgi apparatus, an endoplasmicreticulum, a ribosome, a lysosome, a vacuole, an endocytic vesicle, anexocytic vesicle, a cytoskeleton and a chloroplast) or a subcellularregion (e.g., of one or any combination of a plasma membrane, a cellwall and a ribosomal subunit). In still other aspects, expression of theRNA is controlled by a promoter selected from the group consisting ofone or any combination of an inducible promoter, a cell type-specificpromoter and a signal-specific promoter. In certain aspects, a promoteris an endogenous promoter. In other aspects, a promoter is an exogenouspromoter.

In certain exemplary embodiments, a method of labelling a protein invivo is provided. The method includes the steps of providing a cell thatexpresses an RNA comprising a barcode and that expresses a proteincomprising an RNA binding domain, allowing the RNA and the protein tointeract, reverse transcribing the RNA to produce DNA, circularizing theDNA, and performing RCA to produce an amplicon. The method optionallyincludes the step of detecting the amplicon.

In certain aspects, the protein further comprises a domain thatlocalizes it to a subcellular component. The subcellular component canbe an organelle (e.g., one or any combination of a nucleus, a nucleolus,a mitochondria, a Golgi apparatus, an endoplasmic reticulum, a ribosome,a lysosome, a vacuole, an endocytic vesicle, an exocytic vesicle, acytoskeleton and a chloroplast) or a subcellular region (e.g., of one orany combination of a plasma membrane, a cell wall and a ribosomalsubunit). In other aspects, expression of the RNA is controlled by apromoter selected from the group consisting of one or any combination ofan inducible promoter, a cell type-specific promoter and asignal-specific promoter. In certain aspects, a promoter is anendogenous promoter. In certain aspects, a promoter is an exogenouspromoter.

In certain exemplary embodiments, a method of determining a nucleic acidsequence in situ is provided. The method includes the steps of providinga cell expressing an RNA comprising a barcode, reverse transcribing theRNA to produce DNA, circularizing the DNA, performing RCA to produce anamplicon, and sequencing the amplicon. In certain aspects, the cellfurther expresses a protein comprising an RNA binding domain.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains drawings executed in color.Copies of this patent or patent application publication with the colordrawings will be provided by the Office upon request and payment of thenecessary fee. The foregoing and other features and advantages of thepresent invention will be more fully understood from the followingdetailed description of illustrative embodiments taken in conjunctionwith the accompanying drawings in which:

FIGS. 1A-1B schematically depict sequencing-compatible rolling circleamplification (RCA) amplicons crosslinked to a cell matrix and/orprotein. (1A) A protein of interest is fused to a specific RNA bindingprotein (e.g., MS2, phage N peptides or the like) either at theN-terminus, the C-terminus or internally. A barcode-bearing RNA moleculewith a stem-loop sequence that imparts high specificity binding isco-expressed in the cell. (1B) Cells are fixed and reverse transcriptionfrom internally primed stem loop RNA structures is used to convert RNAto DNA.

FIG. 2 schematically depicts a method for efficiently generating DNAamplicons from bar code-bearing RNA molecules according to certainaspects of the invention. Synthesis of DNA from complementary RNA insitu is improved by using the end of the stem-loop structure, which alsoserves as the recognition site for the RNA binding protein. Afterreverse transcription (RT), RNases are used to remove much of the RNA,while an additional cleavage step is performed using a guide oligo and arestriction enzyme that processes the 5′ end of the DNA for efficientcircularization. RCA is then used to generate tandem copies of the DNA,enabling molecular sequencing in situ with a high signal-to-noise ratio.

FIG. 3 schematically depicts digital images generated by fluorescentsequencing of barcode labels that are combined to create a compositeimage in which all channels and images over time are spatiallyregistered. The composite image contains potential signals at eachpixel. Real signals corresponding to nucleic acid sequences aredistinguishable from objects not of interest (e.g., dirt,autofluorescence and the like) by the nature and/or content of thesequence signals. The nature of sequencing reactions can be programmedto give k signals per time point over N time points. Biological featurescan be labelled with kN unique barcodes.

FIG. 4 schematically depicts the identification of two objects among thepixels of the image by the nature of their sequence patterns, i.e., theyhave signal at each sequencing base in only one channel, sustained overall sequencing reactions. The pixels constituting object A do not matcheach other perfectly, but a custom distance function clusters these assufficiently similar to belong to the same object, and a compositesequence is generated. The pixels constituting object B each shareidentical sequences.

FIG. 5 schematically depicts the identification of objects by matchingthe sequence patterns in all pixels to a reference sequence database.Connected components (pixels) with shared sequences (or with sharedmatches to sequence patterns) are clustered to identify objects. Pixelswithout sequences in the reference sequence database are filtered out ofthe final image (e.g., background, noise, dirt, autofluorescence and thelike). The attributes of each object, such as size, shape and geneticcontent, can be computed and used in downstream analyses.

FIG. 6 schematically depicts neurons that are reconstructed using themethods described herein in which RNA barcodes are expressed in thenuclei or cell bodies, as well as in the synapse. Distant synapses areuniquely linked to the projecting cell body through the RNA barcode. Thenuclear barcode is expressed but not polyadenylated, and is thereforelocalized to the nucleus without coupling to RNA-binding protein. Thesynapse is labelled with RNA barcode coupled to RNA-binding proteindomain fused to a synapse-localizing proteins such as, e.g., neurexin.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The present invention provides methods for detecting biological featuresin situ utilizing nucleic acid barcodes sequences. In certain exemplaryembodiments, a cell expresses an exogenous nucleic acid sequence, e.g.,an RNA sequence, that comprises a barcode. The barcode can serve as alabel for the cell itself, and/or as a label for a subcellularcomponent, e.g., an organelle or subcellular region of the cell. Incertain aspects, the RNA sequence further comprises one or morelocalization sequences that direct RNA to one or more processingpathways (e.g., endogenous and/or exogenous) to localize the RNAsequence such that it can function as a barcode label for subcellular orextracellular features.

As used herein, the term “barcode” refers to a unique oligonucleotidesequence that allows a corresponding nucleic acid sequence (e.g., anoligonucleotide fragment) to be identified, retrieved and/or amplified.In certain embodiments, barcodes can each have a length within a rangeof from 4 to 36 nucleotides, or from 6 to 30 nucleotides, or from 8 to20 nucleotides. In certain exemplary embodiments, a barcode has a lengthof 4 nucleotides. In certain aspects, the melting temperatures ofbarcodes within a set are within 10° C. of one another, within 5° C. ofone another, or within 2° C. of one another. In other aspects, barcodesare members of a minimally cross-hybridizing set. That is, thenucleotide sequence of each member of such a set is sufficientlydifferent from that of every other member of the set that no member canform a stable duplex with the complement of any other member understringent hybridization conditions. In one aspect, the nucleotidesequence of each member of a minimally cross-hybridizing set differsfrom those of every other member by at least two nucleotides. Barcodetechnologies are known in the art and are described in Winzeler et al.(1999) Science 285:901; Brenner (2000) Genome Biol. 1:1 Kumar et al.(2001) Nature Rev. 2:302; Giaever et al. (2004) Proc. Natl. Acad. Sci.USA 101:793; Eason et al. (2004) Proc. Natl. Acad. Sci. USA 101:11046;and Brenner (2004) Genome Biol. 5:240.

As used herein, the term “nucleic acid” includes the term“oligonucleotide” or “polynucleotide” which includes a plurality ofnucleotides. The term “nucleic acid” is intended to include naturallyoccurring nucleic acids and synthetic nucleic acids. The term “nucleicacid” is intended to include single stranded nucleic acids and doublestranded nucleic acids. The term “nucleic acid” is intended to includeDNA and RNA, whether single stranded or double stranded. Nucleotides ofthe present invention will typically be the naturally-occurringnucleotides such as nucleotides derived from adenosine, guanosine,uridine, cytidine and thymidine. When oligonucleotides are referred toas “double-stranded,” it is understood by those of skill in the art thata pair of oligonucleotides exists in a hydrogen-bonded, helical arraytypically associated with, for example, DNA. In addition to the 100%complementary form of double-stranded oligonucleotides, the term“double-stranded” as used herein is also meant to include those formwhich include such structural features as bulges and loops (see Stryer,Biochemistry, Third Ed. (1988), incorporated herein by reference in itsentirety for all purposes). As used herein, the term “polynucleotide”refers to a strand of nucleic acids that can be a variety of differentsizes. Polynucleotides may be the same size as an oligonucleotide, ormay be two-times, three-times, four-times, five-times, ten-times, orgreater than the size of an oligonucleotide.

Oligonucleotides and/or polynucleotides may be isolated from naturalsources or purchased from commercial sources. Oligonucleotide and/orpolynucleotide sequences may be prepared by any suitable method, e.g.,the phosphoramidite method described by Beaucage and Carruthers ((1981)Tetrahedron Lett. 22: 1859) or the triester method according toMatteucci et al. (1981) J. Am. Chem. Soc. 103:3185), both incorporatedherein by reference in their entirety for all purposes, or by otherchemical methods using either a commercial automated oligonucleotidesynthesizer or high-throughput, high-density array methods describedherein and known in the art (see U.S. Pat. Nos. 5,602,244, 5,574,146,5,554,744, 5,428,148, 5,264,566, 5,141,813, 5,959,463, 4,861,571 and4,659,774, incorporated herein by reference in its entirety for allpurposes). Pre-synthesized oligonucleotides may also be obtainedcommercially from a variety of vendors.

As used herein, the term “cellular component” refers to a portion of aprokaryotic or eukaryotic cell. A cellular component includes, forexample, a cellular organelle, including, but not limited to, a nucleus,a nucleolus, a mitochondria, a Golgi apparatus, an endoplasmicreticulum, a ribosome, a lysosome, a vacuole, an endocytic vesicle, anexocytic vesicle, a vacuole, a cytoskeleton, a chloroplast, and thelike. A cellular component can also include a subcellular region,including, but not limited to, a plasma membrane, cell wall, a ribosomalsubunit, transcriptional machinery, cell projections, and the like.

In certain embodiments, cells expressing an exogenous RNA sequence alsoexpress one or more polypeptides comprising an RNA binding domain. RNAbinding domains include four main families: RNA recognition motifs(RRMs), zinc fingers, KH domains and double-stranded RNA binding motifs(dsRBMs). (For a review, see Clery and Allain in Madam Curie BioscienceDatabase (2011), found at the ncbi[dot]nlm[dot]nih[dot]gov website.)Exemplary RNA binding domains include, but are not limited to, MS2,phage N peptides (such as, e.g., lambda phage or P22 phage N-peptides),and the like. A database of DNA binding domains suitable for use in thepresent invention can be found at the websiterbpdb[dot]ccbr[dot]utoronto[dot]ca.

In certain aspects, the polypeptide is a nuclear, cytosolic ortransmembrane protein or a portion thereof (e.g., a polypeptide), fusedto one or more RNA binding domains, such that the RNA sequence canfunction as a barcode label for the fusion protein, allowing for highlyparallel detection of proteins. The cellular origin of eachRNA-barcode-bound fusion protein can be identified by sequencing theassociated RNA barcode.

As used herein, the terms “peptide” and “polypeptide” include compoundsthat consist of two or more amino acids that are linked by means of apeptide bond. Peptides and polypeptides may have a molecular weight ofless than 10,000 Daltons, less than 5,000 Daltons, or less than 2,500Daltons. The terms “peptide” and “polypeptide” also include compoundscontaining both peptide and non-peptide components, such aspseudopeptide or peptidomimetic residues or other non-amino acidcomponents. Such compounds containing both peptide and non-peptidecomponents may also be referred to as a “peptide analogue” or a“polypeptide analogue.”

As used herein, the term “protein” includes compounds that consist ofamino acids arranged in a linear chain and joined together by peptidebonds between the carboxyl and amino groups of adjacent amino acidresidues.

As used herein, the terms “attach” or “bind” refer to both covalentinteractions and noncovalent interactions. A covalent interaction is achemical linkage between two atoms or radicals formed by the sharing ofa pair of electrons (i.e., a single bond), two pairs of electrons (i.e.,a double bond) or three pairs of electrons (i.e., a triple bond).Covalent interactions are also known in the art as electron pairinteractions or electron pair bonds. Noncovalent interactions include,but are not limited to, van der Waals interactions, hydrogen bonds, weakchemical bonds (i.e., via short-range noncovalent forces), hydrophobicinteractions, ionic bonds and the like. A review of noncovalentinteractions can be found in Alberts et al., in Molecular Biology of theCell, 3d edition, Garland Publishing, 1994, incorporated herein byreference in its entirety for all purposes.

In certain exemplary embodiments, biological features can be labelled asdescribed herein using 4N unique RNA barcodes, wherein N is sequencelength. Cellular components labelled as described herein can beidentified by sequencing one or more associated RNA barcode labels. Whena transmembrane protein is labelled, the membrane borders of 4N (whereinN is sequence length) cells can uniquely be identified using the RNAbarcode for highly multiplexed membrane segmentation.

In certain exemplary embodiments, one or more components involved withintracellular or intercellular communication (e.g., involved withsynapse formation, vesicle trafficking and the like) can be labelled byexpressing a fusion protein encoding a localization domain specific toboth the component and to an RNA binding domain in a cell. The expressedRNA barcode label can bind the fusion protein and be subsequentlytransported to a cellular component (e.g., organelle or subcellularregion) of interest.

In accordance with certain examples, methods of sequencing barcodes insitu within an organism (e.g., in a cell or subcellular component (e.g.,an organelle or a subcellular region)) are provided. General sequencingmethods known in the art, such as sequencing by extension withreversible terminators, fluorescent in situ sequencing (FISSEQ),pyrosequencing, massively parallel signature sequencing (MPSS) and thelike (described in Shendure et al. (2004) Nat. Rev. 5:335, incorporatedherein by reference in its entirety), are suitable for use with thematrix in which the nucleic acids are present. Reversible terminationmethods use step-wise sequencing-by-synthesis biochemistry that coupledwith reversible termination and removable fluorescence (Shendure et al.supra and U.S. Pat. Nos. 5,750,341 and 6,306,597, incorporated herein byreference.

FISSEQ is a method whereby DNA is extended by adding a single type offluorescently-labelled nucleotide triphosphate to the reaction, washingaway unincorporated nucleotide, detecting incorporation of thenucleotide by measuring fluorescence, and repeating the cycle. At eachcycle, the fluorescence from previous cycles is bleached or digitallysubtracted or the fluorophore is cleaved from the nucleotide and washedaway. FISSEQ is described further in Mitra et al. (2003) Anal. Biochem.320:55, incorporated herein by reference in its entirety for allpurposes.

Pyrosequencing is a method in which the pyrophosphate (PPi) releasedduring each nucleotide incorporation event (i.e., when a nucleotide isadded to a growing polynucleotide sequence). The PPi released in the DNApolymerase-catalyzed reaction is detected by ATP sulfurylase andluciferase in a coupled reaction which can be visibly detected. Theadded nucleotides are continuously degraded by a nucleotide-degradingenzyme. After the first added nucleotide has been degraded, the nextnucleotide can be added. As this procedure is repeated, longer stretchesof the template sequence are deduced. Pyrosequencing is describedfurther in Ronaghi et al. (1998) Science 281:363, incorporated herein byreference in its entirety for all purposes.

MPSS utilizes ligation-based DNA sequencing simultaneously onmicrobeads. A mixture of labelled adaptors comprising all possibleoverhangs is annealed to a target sequence of four nucleotides. Thelabel is detected upon successful ligation of an adaptor. A restrictionenzyme is then used to cleave the DNA template to expose the next fourbases. MPSS is described further in Brenner et al. (2000) Nat. Biotech.18:630, incorporated herein by reference in its entirety for allpurposes.

According to certain aspects, the barcodes within the organism orportion thereof can be interrogated in situ using methods known to thoseof skill in the art including fluorescently labelledoligonucleotide/DNA/RNA hybridization, primer extension with labelledddNTP, sequencing by ligation and sequencing by synthesis. Ligatedcircular padlock probes described in Larsson, et al., (2004), Nat.Methods 1:227-232 can be used to detect multiple sequence targets inparallel, followed by either sequencing-by-ligation, -synthesis or-hybridization of the barcode sequences in the padlock probe to identifyindividual targets.

According to one aspect, methods described herein produce a threedimensional nucleic acid amplicon within an organism or portion thereofwhich is stable, long-lasting and resistant, substantially resistant orpartially resistant to enzymatic or chemical degradation. The threedimensional nucleic acid amplicon can be repeatedly interrogated usingstandard probe hybridization and/or fluorescence based sequencing. Thethree dimensional nucleic acid amplicon can be repeatedly interrogatedwith little or no signal degradation, such as after more than 50 cycles,and with little position shift, such as less than 1 μm per amplicon.

In certain aspects, the fusion protein substitutes for traditionalreporter proteins, such as fluorescent reporter proteins (e.g., greenfluorescent protein (GFP), mCherry, and the like) in fixed cells toperform multiplexed protein localization studies, in which barcodesequences, rather than a specific fluorescent signal, define the label.In certain aspects, the fusion protein can substitute or complementimmunocytochemistry, in which barcode sequences, rather than a limitedrange of colors from secondary antibodies, are used to define the label.

In certain exemplary embodiments, digital images are generated byfluorescent sequencing of barcode labels that are combined to create acomposite image, in which all channels and images over time arespatially registered. The composite image would then contain potentialsignals at each pixel, with real signals corresponding to nucleic acidsequences, which are distinguishable from objects not of interest (e.g.dirt, autofluorescence, and the like) by the nature and/or content ofthe sequence signals.

The nature of expected sequence patterns and the space of potentialsequence patterns encompassing the barcode labels serve as a prioriinformation in object-based image analysis algorithms to identifyobjects and measure object attributes. Object identification does notrely on algorithms utilizing intensity-based thresholds, highsignal-to-noise ratio, or other object features such as shape. Thus, itis much more sensitive for quantitative detection of molecular analytesor cellular features.

The variable region of an RNA comprising a barcode sequence may begenerated randomly or may be designed. Variable regions can beconstructed using nucleic acid synthesis methods or in vivo byrecombination. An RNA comprising a barcode sequence can contain‘error-correcting’ sequences to compensate for a possible sequencingerror. An RNA comprising a barcode sequence may contain on or more RNAlocalization signals to the direct the cell to localize the RNA barcodemolecules to specific subcellular and/or extracellular regions. An RNAcomprising a barcode sequence can be polyadenylated to promote efficientnuclear export.

In certain exemplary embodiments, RNA-binding proteins as describedfurther herein (e.g., MS2, lambda N peptide, P22 N peptide, and thelike) or a portion thereof are fused in frame to a protein of interestat the N-terminus or the C-terminus end. These peptides are capable ofbinding their cognate sequence (e.g., a conserved RNA hairpin stemsequences) with high affinity. A protein of interest can be cytosolic,nuclear, or membrane-spanning, bearing a protein localization signal(i.e. cadherin, synapsin, histone, transcription factors). A protein ofinterest can be expressed by integrating or epi-chromosomal expressionvectors delivered, e.g., by transfection or viral infection.

An RNA comprising a barcode sequence may be converted into cDNA byendogenous or exogenous biochemical means. The 3′ end of an RNAcomprising a barcode sequence can contain an RNA stem loop structureenabling efficient self-primed cDNA synthesis when cells are fixed andtreated with a reverse transcription reaction mixture. The RNA:DNAhybrid formed after reverse transcription can be enzymatically processedusing a combination nucleases and/or restriction enzymes, leaving singlestranded cDNA of a fixed length, which can then be circularized andamplified by rolling circle amplification. The 3′ an RNA comprising abarcode sequence end of the transcript can contain a RNA stem loopstructure necessary for binding to e.g., MS2, phage N peptides, or anyother sequence specific peptide domains.

In certain exemplary embodiments, an RNA:DNA complex is degraded and/orprocessed to yield a 5′ phosphorylated single-stranded DNA molecule,allowing the cDNA barcode to be circularized, such as by enzymes likeCircLigase. Rolling circle amplification can then be used to generatemultiple tandem copies of the barcode in situ. Aminoallyl dUTP andcrosslinkers can be to immobilize the amplicons, e.g., within anorganism (e.g., in a cell or cellular component (e.g., an organelle or asubcellular region)). A primer complementary to the constant region ofthe barcode may be used to prime rolling circle amplification.

Certain aspects of the invention pertain to vectors, such as, forexample, expression vectors. As used herein, the term “vector” refers toa nucleic acid sequence capable of transporting another nucleic acid towhich it has been linked. One type of vector is a “plasmid,” whichrefers to a circular double stranded DNA loop into which additional DNAsegments can be ligated. Another type of vector is a viral vector,wherein additional DNA segments can be ligated into the viral genome. Byway of example, but not of limitation, a vector of the invention can bea single-copy or multi-copy vector, including, but not limited to, a BAC(bacterial artificial chromosome), a fosmid, a cosmid, a plasmid, asuicide plasmid, a shuttle vector, a P1 vector, an episome, YAC (yeastartificial chromosome), a bacteriophage or viral genome, or any othersuitable vector. The host cells can be any cells, including prokaryoticor eukaryotic cells, in which the vector is able to replicate.

Certain vectors are capable of autonomous replication in a host cellinto which they are introduced (e.g., bacterial vectors having abacterial origin of replication and episomal mammalian vectors). Othervectors (e.g., non-episomal mammalian vectors) are integrated into thegenome of a host cell upon introduction into the host cell, and therebyare replicated along with the host genome. Moreover, certain vectors arecapable of directing the expression of genes to which they areoperatively linked. Such vectors are referred to herein as “expressionvectors.” In general, expression vectors of utility in recombinant DNAtechniques are often in the form of plasmids. In the presentspecification, “plasmid” and “vector” can be used interchangeably.However, the invention is intended to include such other forms ofexpression vectors, such as viral vectors (e.g., replication defectiveretroviruses, adenoviruses and adeno-associated viruses), which serveequivalent functions.

In certain exemplary embodiments, an exogenous nucleic acid describedherein (e.g., a nucleic acid sequence encoding an RNA having a barcodesequence and/or a nucleic acid sequence encoding a polypeptide (e.g., afusion protein)) is expressed in bacterial cells using a bacterialexpression vector such as, e.g., a fosmid. A fosmid is a cloning vectorthat is based on the bacterial F-plasmid. The host bacteria willtypically only contain one fosmid molecule, although an induciblehigh-copy ori can be included such that a higher copy number can beobtained (e.g., pCC1FOS™, pCC2FOS™). Fosmid libraries are particularlyuseful for constructing stable libraries from complex genomes. Fosmidsand fosmid library production kits are commercially available(EPICENTRE® Biotechnologies, Madison, Wis.). For other suitableexpression systems for both prokaryotic and eukaryotic cells seechapters 16 and 17 of Sambrook, J., Fritsh, E. F., and Maniatis, T.Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring HarborLaboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y., 1989.

In certain exemplary embodiments, the recombinant expression vectorscomprise a nucleic acid sequence in a form suitable for expression ofthe nucleic acid sequence in a host cell, which means that therecombinant expression vectors include one or more regulatory sequences,selected on the basis of the host cells to be used for expression, whichis operatively linked to the nucleic acid sequence to be expressed.Within a recombinant expression vector, “operably linked” is intended tomean that the foreign nucleic acid sequence encoding a plurality ofribonucleic acid sequences described herein is linked to the regulatorysequence(s) in a manner which allows for expression of the nucleic acidsequence. In certain aspects, operably linked nucleic acid sequences arephysically linked, using e.g., fusion RNAs and/or fusion proteinswithout splicing and/or cleavage of the endogenous product andrecombinant nucleic acid sequences. The term “regulatory sequence” isintended to include promoters, enhancers and other expression controlelements (e.g., polyadenylation signals). Such regulatory sequences aredescribed, for example, in Goeddel; Gene Expression Technology: Methodsin Enzymology 185, Academic Press, San Diego, Calif. (1990). It will beappreciated by those skilled in the art that the design of theexpression vector can depend on such factors as the choice of the hostcell to be transformed, the level of expression of protein desired, andthe like.

Another aspect of the invention pertains to host cells into which arecombinant expression vector of the invention has been introduced. Theterms “host cell” and “recombinant host cell” are used interchangeablyherein. It is understood that such terms refer not only to theparticular subject cell but to the progeny or potential progeny of sucha cell. Because certain modifications may occur in succeedinggenerations due to either mutation or environmental influences, suchprogeny may not, in fact, be identical to the parent cell, but are stillincluded within the scope of the term as used herein.

Cells according to the present disclosure include any cell into whichforeign nucleic acids can be introduced and expressed as describedherein. It is to be understood that the basic concepts of the presentdisclosure described herein are not limited by cell type. Cellsaccording to the present disclosure include eukaryotic cells,prokaryotic cells, animal cells, plant cells, insect cells, fungalcells, archaeal cells, eubacterial cells, a virion, a virosome, avirus-like particle, a parasitic microbe, an infectious protein and thelike. Cells include eukaryotic cells such as yeast cells, plant cells,and animal cells. Particular cells include bacterial cells. Othersuitable cells are known to those skilled in the art.

Foreign nucleic acids (i.e., those which are not part of a cell'snatural nucleic acid composition) may be introduced into a cell usingany method known to those skilled in the art for such introduction. Suchmethods include transfection, transduction, infection (e.g., viraltransduction), injection, microinjection, gene gun, nucleofection,nanoparticle bombardment, transformation, conjugation, by application ofthe nucleic acid in a gel, oil, or cream, by electroporation, usinglipid-based transfection reagents, or by any other suitable transfectionmethod. One of skill in the art will readily understand and adapt suchmethods using readily identifiable literature sources.

As used herein, the terms “transformation” and “transfection” areintended to refer to a variety of art-recognized techniques forintroducing foreign nucleic acid into a host cell, including calciumphosphate or calcium chloride co-precipitation, DEAE-dextran-mediatedtransfection, lipofection (e.g., using commercially available reagentssuch as, for example, LIPOFECTIN® (Invitrogen Corp., San Diego, Calif.),LIPOFECTAMINE® (Invitrogen), FUGENE® (Roche Applied Science, Basel,Switzerland), JETPEI™ (Polyplus-transfection Inc., New York, N.Y.),EFFECTENE® (Qiagen, Valencia, Calif.), DREAMFECT™ (OZ Biosciences,France) and the like), or electroporation (e.g., in vivoelectroporation). Suitable methods for transforming or transfecting hostcells can be found in Sambrook, et al. (Molecular Cloning: A LaboratoryManual. 2nd, ed., Cold Spring harbor Laboratory, Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y., 1989), and other laboratorymanuals.

Typically, the vector or plasmid contains sequences directingtranscription and translation of a relevant gene or genes, a selectablemarker, and sequences allowing autonomous replication or chromosomalintegration. Suitable vectors comprise a region 5′ of the gene whichharbors transcriptional initiation controls and a region 3′ of the DNAfragment which controls transcription termination. Both control regionsmay be derived from genes homologous to the transformed host cell,although it is to be understood that such control regions may also bederived from genes that are not native to the species chosen as aproduction host.

Initiation control regions or promoters, which are useful to driveexpression of the relevant pathway coding regions in the desired hostcell are numerous and familiar to those skilled in the art. Virtuallyany promoter capable of driving these genetic elements is suitable forthe present invention including, but not limited to, lac, ara, tet, trp,IPL, IPR, T7, tac, and trc (useful for expression in Escherichia coliand Pseudomonas); the amy, apr, npr promoters and various phagepromoters useful for expression in Bacillus subtilis, and Bacilluslicheniformis; nisA (useful for expression in gram positive bacteria,Eichenbaum et al. Appl. Environ. Microbiol. 64(8):2763-2769 (1998)); andthe synthetic P11 promoter (useful for expression in Lactobacillusplantarum, Rud et al., Microbiology 152:1011-1019 (2006)). Terminationcontrol regions may also be derived from various genes native to thepreferred hosts.

In certain exemplary embodiments, an RNA comprising a barcode sequencecan be expressed through transcription. Endogenous or exogenouspromoters, such as U6 or H1, can drive expression of the RNA comprisinga barcode sequence. The RNA comprising a barcode sequence may contain acommon region for primer-based amplification and/or sequencing. The termRNA barcode may refer to a variable region alone or to both a variableand a common region, since in some instances the common region is usedto provide a read-out of the variable region.

In certain exemplary embodiments, an RNA comprising a barcode sequencecan be encoded by a genomic locus. In other exemplary embodiments, anRNA comprising a barcode sequence can be encoded by a vector. In certainaspects, an expression module is present in a fusion protein expressionvector. In other exemplary embodiments, an RNA comprising a barcodesequence is delivered directly to a cell by transfection, in which asingle RNA barcode oligonucleotide or a library of RNA barcodeoligonucleotides is added exogenously.

Expression of an RNA comprising a barcode sequence can besignal-dependent and/or context-specific. For example, celltype-specific or signal-specific promoters can be used to express an RNAcomprising a barcode sequence in a desired population of the cells sothat only cellular components and/or proteins in responsive cells arelabelled with the RNA comprising a barcode sequence. Expression of anRNA comprising a barcode sequence can be inducible (e.g., withdoxycycline) in order to avoid toxic effects of prolonged singlestranded RNA overexpression.

Certain vectors are capable of replicating in a broad range of hostbacteria and can be transferred by conjugation. The complete andannotated sequence of pRK404 and three related vectors-pRK437, pRK442,and pRK442(H) are available. These derivatives have proven to bevaluable tools for genetic manipulation in gram negative bacteria (Scottet al., Plasmid 50(1):74-79 (2003)). Several plasmid derivatives ofbroad-host-range Inc P4 plasmid RSF1010 are also available withpromoters that can function in a range of gram negative bacteria.Plasmid pAYC36 and pAYC37, have active promoters along with multiplecloning sites to allow for the heterologous gene expression in gramnegative bacteria.

Chromosomal gene replacement tools are also widely available. Forexample, a thermosensitive variant of the broad-host-range repliconpWV101 has been modified to construct a plasmid pVE6002 which can beused to create gene replacement in a range of gram positive bacteria(Maguin et al., J. Bacteriol. 174(17):5633-5638 (1992)). Additionally,in vitro transposomes are available to create random mutations in avariety of genomes from commercial sources such as EPICENTRE® (Madison,Wis.).

Vectors useful for the transformation of E. coli are common andcommercially available. For example, the desired genes may be isolatedfrom various sources, cloned onto a modified pUC19 vector andtransformed into E. coli host cells. Alternatively, the genes encoding adesired biosynthetic pathway may be divided into multiple operons,cloned into expression vectors, and transformed into various E. colistrains.

Features or objects may be of a biological nature, such as molecules,subcellular compartments, projections, cells, groups of cells, regionsof tissue, tissues, or organs. Biological features may be made to havethe characteristics described above by sequencing synthetic or natural,endogenous or exogenous, nucleic acid molecules spatially organized byany method, familiar to those with skill in the art.

Analysis of objects using methods described herein may be combined withor compared to other images of the sample that have been stained withmembrane- and organelle-specific dyes, antibodies, or reporter proteins.

In certain embodiments, nucleic acids are those found naturally in abiological sample, such as a cell or tissue.

Embodiments of the present invention are directed to methods ofamplifying nucleic acids in situ within an organism or portion thereof(e.g., cell (e.g., cellular component, e.g., organelle and/orsubcellular region), tissue, organ or the like) by contacting thebarcode with reagents and under suitable reaction conditions sufficientto amplify the barcode. According to one aspect, the organism or portionthereof is rendered porous or permeable to allow migration of reagentsinto the matrix to contact the barcode. In certain aspects, barcodes areamplified by selectively hybridizing an amplification primer to anamplification site at the 3′ end of the barcode using conventionalmethods. Amplification primers are 6 to 100, and even up to 1,000,nucleotides in length, but typically from 10 to 40 nucleotides, althougholigonucleotides of different length are of use.

Typically, selective hybridization occurs when two nucleic acidsequences are substantially complementary, i.e., at least about 65% 75%,80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% 99%, 99.1%, 99.2%,99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100% complementaryover a stretch of at least 14 to 25 nucleotides. See Kanehisa, M., 1984,Nucleic Acids Res. 12: 203, incorporated herein by reference in itsentirety for all purposes.

Overall, five factors influence the efficiency and selectivity ofhybridization of the primer to a second nucleic acid molecule. Thesefactors, which are (i) primer length, (ii) the nucleotide sequenceand/or composition, (iii) hybridization temperature, (iv) bufferchemistry and (v) the potential for steric hindrance in the region towhich the primer is required to hybridize, are important considerationswhen non-random priming sequences are designed.

There is a positive correlation between primer length and both theefficiency and accuracy with which a primer will anneal to a targetsequence; longer sequences have a higher Tm than do shorter ones, andare less likely to be repeated within a given target sequence, therebycutting down on promiscuous hybridization. Primer sequences with a highG-C content or that comprise palindromic sequences tend toself-hybridize, as do their intended target sites, since unimolecular,rather than bimolecular, hybridization kinetics are generally favored insolution; at the same time, it is important to design a primercontaining sufficient numbers of G-C nucleotide pairings to bind thetarget sequence tightly, since each such pair is bound by three hydrogenbonds, rather than the two that are found when A and T bases pair.Hybridization temperature varies inversely with primer annealingefficiency, as does the concentration of organic solvents, e.g.,formamide, that might be included in a hybridization mixture, whileincreases in salt concentration facilitate binding. Under stringenthybridization conditions, longer probes hybridize more efficiently thando shorter ones, which are sufficient under more permissive conditions.Stringent hybridization conditions typically include salt concentrationsof less than about 1M, more usually less than about 500 mM andpreferably less than about 200 mM. Hybridization temperatures range fromas low as 0° C. to greater than 22° C., greater than about 30° C., and(most often) in excess of about 37° C. Longer fragments may requirehigher hybridization temperatures for specific hybridization. As severalfactors affect the stringency of hybridization, the combination ofparameters is more important than the absolute measure of any one alone.Hybridization conditions are known to those skilled in the art and canbe found in Current Protocols in Molecular Biology, John Wiley & Sons,N.Y. (1989), 6.3.1-6.3.6, incorporated herein by reference in itsentirety for all purposes.

Primers are designed with the above first four considerations in mind.While estimates of the relative merits of numerous sequences are madementally, computer programs have been designed to assist in theevaluation of these several parameters and the optimization of primersequences (see, e.g., Hoover et al. (2002) Nucleic Acids Res. 30:e43,and Rouillard et al. (2004) Nucleic Acids Res. 32:W176, incorporated byreference herein in their entirety for all purposes).

In accordance with an additional aspect, kits are provided. In oneaspect, the kits comprise a cell described herein, and optionally,instructions for use.

According to one aspect, nucleic acids are modified to incorporate afunctional moiety for attachment to a matrix. The functional moiety canbe covalently crosslinked, copolymerize with or otherwise non-covalentlybound to the matrix. The functional moiety can react with a crosslinker.The functional moiety can be part of a ligand-ligand binding pair. DNTPor dUTP can be modified with the functional group, so that the functionmoiety is introduced into the DNA during amplification. A suitableexemplary functional moiety includes an amine, acrydite, alkyne, biotin,azide, and thiol. In the case of crosslinking, the functional moiety iscrosslinked to modified dNTP or dUTP or both. Suitable exemplarycrosslinker reactive groups include imidoester (DMP), succinimide ester(NHS), maleimide (Sulfo-SMCC), carbodiimide (DCC, EDC) and phenyl azide.Crosslinkers within the scope of the present disclosure may include aspacer moiety. Such spacer moieties may be functionalized. Such spacermoieties may be chemically stable. Such spacer moieties may be ofsufficient length to allow amplification of the nucleic acid bound tothe matrix. Suitable exemplary spacer moieties include polyethyleneglycol, carbon spacers, photo-cleavable spacers and other spacers knownto those of skill in the art and the like.

According to one aspect, a matrix-forming material is contacted to aplurality of nucleic acids spatially arrange in three-dimensionsrelative to one another.

Matrix forming materials include polyacrylamide, cellulose, alginate,polyamide, crosslinked agarose, crosslinked dextran or crosslinkedpolyethylene glycol. The matrix forming materials can form a matrix bypolymerization and/or crosslinking of the matrix forming materials usingmethods specific for the matrix forming materials and methods, reagentsand conditions known to those of skill in the art. In certain aspects,the structure of a matrix is static, e.g., the matrix has a stablethree-dimensional state. In other aspects, the matrix is flexible, e.g.,one or more of matrix size, shape, etc. can be altered or modified suchthat higher spatial resolution is achieved and/or additional downstreamanalyses cab be performed, e.g., mass spectroscopy and the like.

According to one aspect, a matrix-forming material can be introducedinto a cell. The cells are fixed with formaldehyde and then immersed inethanol to disrupt the lipid membrane. The matrix forming reagents areadded to the sample and are allowed to permeate throughout the cell. Apolymerization inducing catalyst, UV or functional crosslinkers are thenadded to allow the formation of a gel matrix. The unincorporatedmaterial is washed out and any remaining functionally reactive group isquenched. Exemplary cells include any cell, human or otherwise,including diseased cells or healthy cells. Certain cells include humancells, non-human cells, human stem cells, mouse stem cells, primary celllines, immortalized cell lines, primary and immortalized fibroblasts,HeLa cells and neurons.

According to one aspect, a matrix-forming material can be used toencapsulate a biological sample, such as a tissue sample. Theformalin-fixed embedded tissues on glass slides are incubated withxylene and washed using ethanol to remove the embedding wax. They arethen treated with Proteinase K to permeabilized the tissue. Apolymerization inducing catalyst, UV or functional crosslinkers are thenadded to allow the formation of a gel matrix. The un-incorporatedmaterial is washed out and any remaining functionally reactive group isquenched. Exemplary tissue samples include any tissue samples ofinterest whether human or non-human. Such tissue samples include thosefrom skin tissue, muscle tissue, bone tissue, organ tissue and the like.Exemplary tissues include human and mouse brain tissue sections, embryosections, tissue array sections, and whole insect and worm embryos.

The matrix-forming material forms a three dimensional matrix includingthe plurality of nucleic acids. According to one aspect, thematrix-forming material forms a three dimensional matrix including theplurality of nucleic acids while maintaining the spatial relationship ofthe nucleic acids. In this aspect, the plurality of nucleic acids areimmobilized within the matrix material. The plurality of nucleic acidsmay be immobilized within the matrix material by co-polymerization ofthe nucleic acids with the matrix-forming material. The plurality ofnucleic acids may also be immobilized within the matrix material bycrosslinking of the nucleic acids to the matrix material or otherwisecrosslinking with the matrix-forming material. The plurality of nucleicacids may also be immobilized within the matrix by covalent attachmentor through ligand-protein interaction to the matrix.

According to one aspect, the matrix is porous thereby allowing theintroduction of reagents into the matrix at the site of a nucleic acidfor amplification of the nucleic acid. A porous matrix may be madeaccording to methods known to those of skill in the art. In one example,a polyacrylamide gel matrix is co-polymerized with acrydite-modifiedstreptavidin monomers and biotinylated DNA molecules, using a suitableacrylamide:bis-acrylamide ratio to control the crosslinking density.Additional control over the molecular sieve size and density is achievedby adding additional crosslinkers such as functionalized polyethyleneglycols. According to one aspect, the nucleic acids, which may representindividual bits of information, are readily accessed byoligonucleotides, such as labelled oligonucleotide probes, primers,enzymes and other reagents with rapid kinetics.

According to one aspect, the matrix is sufficiently opticallytransparent or otherwise has optical properties suitable for standardNext Generation sequencing chemistries and deep three dimensionalimaging for high throughput information readout. The Next Generationsequencing chemistries that utilize fluorescence imaging include ABISoLiD (Life Technologies), in which a sequencing primer on a template isligated to a library of fluorescently labelled nonamers with a cleavableterminator. After ligation, the beads are then imaged using four colorchannels (FITC, Cy3, Texas Red and Cy5). The terminator is then cleavedoff leaving a free-end to engage in the next ligation-extension cycle.After all dinucleotide combinations have been determined, the images aremapped to the color code space to determine the specific base calls pertemplate. The overflow is achieved using an automated fluidics andimaging device (i.e. SoLiD 5500 W Genome Analyzer, ABI LifeTechnologies). Another sequencing platform uses sequencing by synthesis,in which a pool of single nucleotide with a cleavable terminator isincorporated using DNA polymerase. After imaging, the terminator iscleaved and the cycle is repeated. The fluorescence images are thenanalyzed to call bases for each DNA amplicons within the flow cell(HiSeq, Illumia).

According to certain aspects, the plurality of nucleic acids may beamplified to produce amplicons by methods known to those of skill in theart. The amplicons may be immobilized within the matrix generally at thelocation of the nucleic acid being amplified, thereby creating alocalized colony of amplicons. The amplicons may be immobilized withinthe matrix by steric factors. The amplicons may also be immobilizedwithin the matrix by covalent or noncovalent bonding. In this manner,the amplicons may be considered to be attached to the matrix. By beingimmobilized to the matrix, such as by covalent bonding or crosslinking,the size and spatial relationship of the original amplicons ismaintained. By being immobilized to the matrix, such as by covalentbonding or crosslinking, the amplicons are resistant to movement orunraveling under mechanical stress.

According to one aspect, the amplicons, such as DNA amplicons, are thencopolymerized and/or covalently attached to the surrounding matrixthereby preserving their spatial relationship and any informationinherent thereto. For example, if the amplicons are those generated fromDNA or RNA within a cell embedded in the matrix, the amplicons can alsobe functionalized to form covalent attachment to the matrix preservingtheir spatial information within the cell thereby providing asubcellular localization distribution pattern.

According to one aspect, a plurality of circular DNA molecules arecovalently linked to one another. The circular DNA molecules are thenamplified using methods known to those of skill in the art, such asisothermal enzymatic amplification one example of which is RCA.According to this aspect, the amplicons are localized near the circularDNA. According to this aspect, the amplicons form a shell around thecircular DNA or otherwise assemble around the circular DNA. Eachcircular DNA may have more than 1000 amplicons surrounding or otherwiseassociated therewith. According to this aspect, the ampliconssurrounding a particular circular DNA provide a high signal intensity,due in part to the number of amplicons and/or detectable labelsassociated with the amplicons.

The amplicons may be functionalized and crosslinked or otherwisecovalently bound together around their associate circular DNA to form aseries or network of tightly bound DNA amplicon shells around eachcircular DNA. The series or network of tightly bound DNA amplicon shellsaround each circular DNA may be assembled onto a three-dimensionalsupport. According to one aspect, the series or network of tightly boundDNA amplicon shells around each circular DNA may be assembled onto athree-dimensional support producing a three dimensional DNA polymer withdefined overall shape, size and amplicon position.

According to one aspect, amplicons are covalently linked without theneed for separate crosslinkers, such as bis-N-succinimidyl-(nonaethyleneglycol) ester. An acrydite moiety, such as a catalyst activated acryditemoiety is introduced at the end of a long carbon spacer (i.e., about C6to about C12) at position 5 of a uracil base a representative formula ofwhich is shown below.

In the formula below, R represents the acrydite spacer moiety attachedto the 5 position of the uracil base.

When copolymerized with bis-acrylamide in the presence of a catalyst, apolymerization reaction takes place, encapsulating the circular DNA withthe amplicons and fixing the amplicons in position. The chemically inertnature of the polymerized mixture allows various downstreamapplications. The spacer can be a carbon chain of between about 2carbons to about 200 carbons. The spacer can be polyethylene glycol. Thelength of the spacer can vary from about 30 angstroms to about 100angstroms and can be of various molecular weights. The spacer can bepermanent or reversible, such as by using UV light, enzymes, chemicalcleavage, etc.

A three dimensional matrix, such as a polyacrylamide gel matrix, can beused to embed a variety of biological structures containingenzymatically or chemically modified DNA or RNA molecules containing anacrydite functional moiety. The non-nucleic acid component isselectively dissolved using detergents, proteases, organic solvents ordenaturants to create a three dimensional matrix that preservesindividual DNA or RNA molecules and their relative spatial location.Examples include embedding cells, healthy and diseased tissues andtissue sections, small model organisms such as worms and insects,bacterial colonies or biofilms, environmental samples containing otherDNA or RNA containing materials or organisms.

In certain exemplary embodiments, an object-based image analysis (OBIA)algorithm is used to analyze barcode sequences. The OBIA algorithmapplies pattern identification and matching sequences to partitionimages into objects and measure object properties, given the objects areproperly labelled with sufficiently long DNA or RNA barcode sequences.The actual sequence profile of an object is a subset of the totalpotential sequence space. Objects are identified through a prioriinformation about the expected sequence patterns and the space ofpotential sequence patterns.

As used herein, a “digital image data” refers to a numericrepresentation of values corresponding to measured signals distributedin two- or three-dimensional space over time. The map may be storedusing raster or vector format. The signals measured are generated usingsequencing methods described above. Sequencing signals are characterizedas a temporal pattern within the digital image data, such that the totalsignal profile is a subset of the total possible signal space. Digitalimage data can be processed using methods such as deconvolution,registration, normalization, projection, and/or any other appropriatemathematical transformations known in the art. Images are registeredover time.

As used herein, the term “pattern identification OBIA” refers to theidentification and characterization of an object within the image databy identifying the temporal pattern using prior information about thenature of expected patterns. According to this aspect of the invention,pixels are identified as objects or spatially clustered into objects byidentifying pixels with the characteristics listed above. According toone aspect of the invention, objects are identified using theexpectation that they consist of one or more spatially correlated pixelswith a particular temporal sequence of signals.

As used herein, the term “pattern matching OBIA” refers to theidentification and characterization of an object within the image databy matching the sequence patterns of individual pixels or compositepatterns of groups of pixels to a reference set of expected patterns. Incertain aspects of the invention, the patterns compared to the referencemay be a subset of all patterns present in the image. In other aspectsof the invention, all patterns in the data may be compared to thereference. According to certain aspects of the invention, patterns inthe data may be compared and matched to the expected reference patternsby search methods and/or computation of distance metrics or probabilityfunctions familiar to those with skill in the art.

A reference characteristic may consist of nucleic acid sequences,including genomic or transcriptomic sequences as well as synthetic,artificial, or programmed sequences of nucleic acids. The referencecharacteristic may consist of any previously known set of patterns withthe characteristics listed above.

Computational tasks related to OBIA are executed using the patternidentification and/or pattern matching methods, including featurerecognition, segmentation, object tracking, object counting, objectdisambiguation, object reconstruction, and spatial classification.Sequence pattern identification and matching described above may be usedfor computational image processing tasks, such as image stitching,registration, filtering, colorization, parameterization, and noisereduction. For instance, objects in the digital image data with patternsnot matched in the reference may be excluded from visualization andsubsequent analysis. Remaining pixels may be false colored, filtered, orotherwise represented as a high-dynamic range image; with dynamic rangesufficient to represent the space of identified sequences. This reducesthe impact of autofluorescence and background noise from cellular debrisin visualization and downstream analysis. Image registration andstitching algorithms can be designed to maximize the number of objectsidentified using methods described above.

Certain exemplary embodiments are directed to the use of computersoftware to automate design and/or interpretation of genomic sequences,mutations, oligonucleotide sequences and the like. Such software may beused in conjunction with individuals performing interpretation by handor in a semi-automated fashion or combined with an automated system. Inat least some embodiments, the design and/or interpretation software isimplemented in a program written in the JAVA programming language. Theprogram may be compiled into an executable that may then be run from acommand prompt in the WINDOWS XP operating system. Unless specificallyset forth in the claims, the invention is not limited to implementationusing a specific programming language, operating system environment orhardware platform.

It is to be understood that the embodiments of the present inventionwhich have been described are merely illustrative of some of theapplications of the principles of the present invention. Numerousmodifications may be made by those skilled in the art based upon theteachings presented herein without departing from the true spirit andscope of the invention. The contents of all references, patents andpublished patent applications cited throughout this application arehereby incorporated by reference in their entirety for all purposes.

The following examples are set forth as being representative of thepresent invention. These examples are not to be construed as limitingthe scope of the invention as these and other equivalent embodimentswill be apparent in view of the present disclosure, figures, tables andaccompanying claims.

Example I RCA Amplicon Analysis

A protein of interest is fused to a specific RNA binding protein and abarcode bearing RNA molecule is co-expressed in the cell (FIG. 1A).Cells are then fixed, and reverse transcribed from internally primedstem loop RNA structures are used to convert RNA to DNA (FIG. 1B). Incertain aspects, the DNA is circularized using CircLigase and amplifiedusing Phi29 DNA polymerase. Crosslinker compatible nucleotides areincorporated during reverse transcription and rolling circleamplification. Crosslinkers can then be used to attach nucleotides to asubcellular component (e.g., the cell matrix and/or one or more proteinsand/or attached to a synthetic three-dimensional support matrix (e.g.,co-polymerized in an acrylamide gel). The single molecule amplicons aresequenced using direct DNA ligation, extension, or hybridization usingfluorescently labelled probes. The sequential images from multiplesequencing or hybridization cycles are used to generate sequencing readsfrom each protein-RNA complex. The barcode sequence is then used toidentify individual proteins and where the RNA is transcribed.

Example II Cell Segmentation

Cells expressing an RNA barcode widely throughout the cell body arelabelled and segmented by using the barcode sequence to identify thespace occupied by each cell.

Example III Multiplex Membrane Labelling

Using a fusion protein encoding membrane-specific proteins and cellsthat bear a single copy of the RNA barcode via site-specificrecombination, a large number of cells are labelled with unique RNAbarcodes localized to the cell membrane inner surface. This information,coupled with the use of complementary membrane dyes or proteins, enablesa large number of cellular membranes to be uniquely identified andsegmented. This allows one of ordinary skill in the art the ability toaccurately assess single cell biology using, e.g., cell culture, tissuesections, and/or developing embryos.

Example IV Brain Synapse Mapping

By fusing the RNA binding domain to one or more pre-synaptic orpost-synaptic proteins (e.g., neurexin, neuroligin, synapsin, NMDAreceptor and the like) along with a cell-specific RNA barcode, thephysical location of individual synapses and their cellular origins areimaged in a high-throughput manner. (See FIG. 6.) Each barcode alsocontains information regarding the identity of fusion proteins, suchthat a proper pairing of pre-synaptic and post-synaptic proteins can beidentified using a co-localization matrix. In certain aspects,expression of the fusion protein and/or RNA barcode isactivity-dependent, such that only those neurons and their synapses thatare functionally active are imaged selectively. Synapses are thenuniquely associated with the cells that generate them.

Example V Monitoring Intra-Cellular and/or Inter-Cellular Trafficking

RNA binding domains are specifically fused to vesicle-specific and/orexosome-specific proteins to track multiple vesicles and/or exosomes totheir originating cells.

What is claimed is:
 1. A method of labelling a subcellular component ina cell comprising the steps of: providing the cell with an RNAcomprising a barcode and a localization sequence that targets the RNA tothe subcellular component wherein the localization sequence localizes tothe subcellular component; reverse transcribing the RNA to produce DNA;and amplifying the DNA to produce amplicons.
 2. The method of claim 1wherein amplifying the DNA includes circularizing the DNA; andperforming rolling circle amplification (RCA) to produce an amplicon. 3.The method of claim 1, further comprising the step of detecting theamplicon.
 4. The method of claim 2, wherein the subcellular component isan organelle or a subcellular region.
 5. The method of claim 4, whereinthe organelle is selected from the group consisting of one or anycombination of a nucleus, a nucleolus, a mitochondria, a Golgiapparatus, an endoplasmic reticulum, a ribosome, a lysosome, a vacuole,an endocytic vesicle, an exocytic vesicle, a cytoskeleton and achloroplast.
 6. The method of claim 4, wherein the subcellular region isselected from the group consisting of one or any combination of a plasmamembrane, a cell wall and a ribosomal subunit.
 7. The method of claim 1,wherein the RNA is provided by expression of the RNA by the cell whichis controlled by a promoter selected from the group consisting of one orany combination of an inducible promoter, a cell type-specific promoterand a signal-specific promoter.
 8. The method of claim 1 wherein the RNAis provided by being delivered directly to the cell.
 9. A method oflabelling a protein in a cell comprising the steps of: providing thecell with an RNA comprising a barcode and a protein comprising an RNAbinding domain and a localization sequence wherein the localizationsequence localizes to the subcellular component and the RNA binds to theRNA binding domain; reverse transcribing the RNA to produce DNA;circularizing the DNA; and performing RCA to produce an amplicon. 10.The method of claim 9, further comprising the step of detecting theamplicon.
 11. The method of claim 9, wherein the subcellular componentis an organelle or a subcellular region.
 12. The method of claim 11,wherein the organelle is selected from the group consisting of one orany combination of a nucleus, a nucleolus, a mitochondria, a Golgiapparatus, an endoplasmic reticulum, a ribosome, a lysosome, a vacuole,an endocytic vesicle, an exocytic vesicle, a cytoskeleton and achloroplast.
 13. The method of claim 11, wherein the subcellular regionis selected from the group consisting of one or any combination of aplasma membrane, a cell wall and a ribosomal subunit.
 14. The method ofclaim 9, wherein the RNA is provided by expression of the RNA by thecell which is controlled by a promoter selected from the groupconsisting of one or any combination of an inducible promoter, a celltype-specific promoter and a signal-specific promoter.
 15. A method oflabelling a protein in a cell comprising the steps of: providing thecell with an RNA comprising a barcode, wherein the RNA binds to an RNAbinding domain of a protein within the cell; reverse transcribing theRNA to produce DNA; circularizing the DNA; performing RCA to produce anamplicon; and sequencing the amplicon.
 16. A method of labelling asubcellular component in vivo comprising the steps of: providing a cellexpressing an RNA comprising a barcode; reverse transcribing the RNA toproduce DNA; circularizing the DNA; and performing rolling circleamplification (RCA) to produce an amplicon.
 17. The method of claim 16,further comprising the step of detecting the amplicon.
 18. The method ofclaim 16, wherein the RNA comprises a localization sequence that targetsthe RNA to the subcellular component.
 19. The method of claim 16,wherein the subcellular component is an organelle or a subcellularregion.
 20. The method of claim 19, wherein the organelle is selectedfrom the group consisting of one or any combination of a nucleus, anucleolus, a mitochondria, a Golgi apparatus, an endoplasmic reticulum,a ribosome, a lysosome, a vacuole, an endocytic vesicle, an exocyticvesicle, a cytoskeleton and a chloroplast.
 21. The method of claim 19,wherein the subcellular region is selected from the group consisting ofone or any combination of a plasma membrane, a cell wall and a ribosomalsubunit.
 22. The method of claim 16, wherein expression of the RNA iscontrolled by a promoter selected from the group consisting of one orany combination of an inducible promoter, a cell type-specific promoterand a signal-specific promoter.
 23. A method of labelling a protein invivo comprising the steps of: providing a cell expressing an RNAcomprising a barcode and expressing a protein comprising an RNA bindingdomain; allowing the RNA and the protein to interact; reversetranscribing the RNA to produce DNA; circularizing the DNA; andperforming RCA to produce an amplicon.
 24. The method of claim 23,further comprising the step of detecting the amplicon.
 25. The method ofclaim 23, wherein the protein further comprises a domain that localizesit to a subcellular component.
 26. The method of claim 23, wherein thesubcellular component is an organelle or a subcellular region.
 27. Themethod of claim 26, wherein the organelle is selected from the groupconsisting of one or any combination of a nucleus, a nucleolus, amitochondria, a Golgi apparatus, an endoplasmic reticulum, a ribosome, alysosome, a vacuole, an endocytic vesicle, an exocytic vesicle, acytoskeleton and a chloroplast.
 28. The method of claim 26, wherein thesubcellular region is selected from the group consisting of one or anycombination of a plasma membrane, a cell wall and a ribosomal subunit.29. The method of claim 23, wherein expression of the RNA is controlledby a promoter selected from the group consisting of one or anycombination of an inducible promoter, a cell type-specific promoter anda signal-specific promoter.
 30. A method of determining a nucleic acidsequence in situ comprising the steps of: providing a cell expressing anRNA comprising a barcode; reverse transcribing the RNA to produce DNA;circularizing the DNA; performing RCA to produce an amplicon; andsequencing the amplicon.
 31. The method of claim 30, wherein the cellfurther expresses a protein comprising an RNA binding domain.